1 files changed, 19 insertions, 0 deletions
diff --git a/source/blender/draw/engines/gpencil/shaders/gpencil_stroke_frag.glsl b/source/blender/draw/engines/gpencil/shaders/gpencil_stroke_frag.glsl
index 73baacb35d4..0f1665b73c2 100644
--- a/source/blender/draw/engines/gpencil/shaders/gpencil_stroke_frag.glsl
+++ b/source/blender/draw/engines/gpencil/shaders/gpencil_stroke_frag.glsl
@@ -8,6 +8,12 @@ uniform vec4 colormix;
 uniform float mix_stroke_factor;
 uniform int shading_type[2];
 
+uniform int fade_layer;
+uniform float fade_layer_factor;
+uniform bool fade_ob;
+uniform vec3 fade_color;
+uniform float fade_ob_factor;
+
 in vec4 mColor;
 in vec2 mTexCoord;
 in vec2 uvfac;
@@ -88,4 +94,17 @@ void main()
   if (fragColor.a < 0.0035) {
     discard;
   }
+
+  /* Apply paper opacity */
+  if (fade_layer == 1) {
+    /* Layer is below, mix with background. */
+    fragColor.rgb = mix(fade_color.rgb, fragColor.rgb, fade_layer_factor);
+  }
+  else if (fade_layer == 2) {
+    /* Layer is above, change opacity. */
+    fragColor.a *= fade_layer_factor;
+  }
+  else if (fade_ob == true) {
+    fragColor.rgb = mix(fade_color.rgb, fragColor.rgb, fade_ob_factor);
+  }
 }